Flat display tube and method



' Sept. 29, 1970 J. T. HARDEN, JR

FLAT DISPLAY TUBE AND METHOD 5 Sheets-Sheet J Filed June 25, 196e 1 Tm uM000000000000000000000v w ATTORNEY 3-1` 29, 19?@ J. T. HARDEN, JR

FLAT DISPLAY TUBE AND METHOD 5 Sheets-Sheet 2 Filed June 25, 1968 29,1970 J. T. HARDEN, JR

FLAT DISPLAY TUBE AND METHOD Filed June 25, 1968 5 Sheets-Sheet 3 J. T.HARDEN, JR

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vToEU V Y A -53 AVAVAVAVVV? RING COUNTER CIRCUIT FLAT DISPLAY TUBE ANDMETHOD #Aw Www A Filed June. 25, 1968 Sandston, Va. 23150 Filed June 25,1968, Ser. No. 739,819 Int. Cl. H01j 29/50, 29/72 US. Cl. 315-13 20Claims ABSTRACT F THE DISCLOSURE A thin flat display tube in which aplurality of individual electron beams corresponding in number to thenumber of horizontal lines desired in a display are sequentiallyprojected into a at narrow space and deflected onto a display screen.Such individual beams are produced by an elongated or linear cathodecapable of controlled emission of electrons from selected points to formbeams, each of which is controlled by electrostatically and sequentiallycontrolling the acceleration and focusing of the pencil beam segments.Each beam is intensity modulated in accordance with image informationcontained in a received television signal, for example, or by other datato be displayed and/ or controlled. Consult the specification for otherfeatures and details.

This invention is related to flat television display tubes, and, moreparticularly, to flat or shallow depth image reproduction tubes and beamgeneration and scanning systems therefore.

In most known short depth or flat cathode ray display tubes (c g.,envelope, electron source, accelerating and deecting structures anddisplay screen) an electron beam is aimed along an edge of the displayscreen past a first series of deflection plates. Deflection of a beaminto the space between the display screen and a second set of deflectionplates is effected by potentials on one of the first deflection platesand impingement of the deflected beam under the display screen iseffected by a potential on the second set of deflection plates. Thepoint of impingement can be varied continuously by sequential variationof potentials on the respective deflection plates to produce, forexample, a conventional television raster. Tubes generally of this typeare disclosed in Aiken Pat. 2,795,731 and several beams may becontrolled in a corresponding manner for control of color displays.

Multi-beam tubes are also disclosed in the patent literature as inRoberts Pat. 2,858,464. In Roberts patent the beam forming structurecomprises an elongated cathode in a perforated or slotted tubular memberwhich produces a plurality of beams or a sheet of electrons. A secondtubular structure having a series of perforations angularly disposedwith respect to the perforations or slot in the first tubular membersurrounds the first tubular member and a deflection field is utilized todeect all electrons (beams or sheet) to cause sequential aligning ofbeams or segments of the sheet of electrons with the second series ofperforations.

Objects of the present invention include providing improvements in thin,flat display tubes, an improved multibeam scanning device and method,primarily for use in flat display tubes and devices.

In accordance with the present invention, instead of it projecting oneor several beams along the edge of the display area and thenmanipulating the beam for horizontal and vertical traverse of thedisplay screen, a plurality of individual beams are generated, one foreach line of a conventional television display raster by means of alinear cathode ray gun structure having means for individually focusingeach individual beams and in which intensity control is effected byincreasing or decreasing the bias on the emission electrode. Thus, theinvention incorporates 3,53l8l Patented Sept. 29, 1970 a unique scanningdevice having a plurality of individualized electron beams eachindividually capable of being electrostatically controlled, focused, andaccelerated into an area of the tube for deflection onto a fluorescentscreen. The screen may be for direct View in the sense that the lightproduced is visible from the surface of the phosphor struck by thescreen thereby reducing the energy requirements for a high light output.In addition, the scanning structure per se may be oriented so as toproject one or a plurality of individualized beams along a path suchthat as the spot of light is caused to traverse a line of impingement onthe display screen, the angle of impingement is substantially constantto maintain the shape of the light spot produced substantially constant.

These and other features, objects and advantages of the invention willbecome apparent from the following description taken with theaccompanying drawings in which:

FIG. l is a prospective view of a shallow depth fiat display tube partlycut-away and illustrating the invention;

FIG. 2, 3, 4, 5, and 6 are exploded perspective views of amulti-electron beam forming, focusing and accelerating structureincorporating the invention;

FIGS. 7 and 8 are diagrammatical cross sectional views of a fiat displaytube incorporating the invention;

FIGS. 9 and 10 are illustrations of a further embodiment of theinvention;

FIG. 1l, taken with the wave form diagrams of FIGS. l2, 13 and 14illustrate another aspect of the invention;

FIGS. l5-2() inclusive, illustrate a direct view application of theinvention;

FIG. 2l is a diagrammatic showing of input circuitry and devices for usewith a at display device incorporating the invention;

FIG. 22 is a circuit diagram of a shift counter circuit and outputconnections thereto for controlling the grid structure of the scanningdevice of this invention, and

FIGS. 23, 24, 25A, 25B, and 25C inclusive, illustrate one application ofthe invention to a color display.

The embodiment of the invention as illustrated in FIG. 1 comprises anenvelope 20 which may be of glass, which may be made from two shallowshaped sections in the forms of shallow rectangular trays fused togetheralong the contacting edges (not shown). Face plate 21 constitutes theviewing area of the tube and has the inner wall thereof a conventionalphosphor coating 22 which serves as the viewing screen. The screen maybe a simple phosphor or a combination of phosphors responsive toelectron bombardment by scanning electron beam or beams to produce lightand, unless otherwise noted, it will be assumed that such phosphors andscreen structures are conventional.

Cathode 2S is an elongated indirectly heated emission cylinder (heatingelement not shown) having a conventional electron emissive coatingthereon such as an oxide type material, and capable of emittingelectrons along its length. Alternatively, the heating element itselfmay be coated with an oxide coating (barium or strontium oxide, forexample) to constitute the cathode. Spaced from cathode 25 are a seriesof emission control grids 26 coacting with a slotted emission controlplate 27, slot 28 in plate 27 having a length substantially along thelength of cathode 25. Grids 26 and slotted control plate 27 areeffective when proper potentials are applied thereto, as describedlater, to effectively cut off emission from the cathode except for aselected area or point Where emission is desired. Further, this gridcontrol structure is capable of controlling emission from any pointalong the length of the cathode or from several points from the entirelength of the cathode simultaneously, if this be desired. Thus, there isno significant loss of energy as the beam dividing srtucture is capableof controlled emission along its length. While this 3 control functionand structure effectively turns olf the rest of the cathode emissionwhile emission is occurring at only one point. It will be apparent thatgroups of grid elements may be assigned independent display controlfunctions and, accordingly, may lbe controlled independently, as groups,with a separate control plate therefor.

Emitted electrons drawn from the region surrounding the cathode to theemission grid plate control structure by virtue of positive potentialplaced upon the emission grid, travel toward the emission grid and gainvelocity and momentum. When electrons reach the emission grid, a greatnumber of electrons strike the grid and are retained but some travelthrough the vertical slit or slot 28. Spaced from slot 28 is a focusingand accelerating assembly 29 which contains an individual focusing andaccelerating structure for each individual beam passing through slot 28.The focusing and accelerating structure electrostatically focuses eachbeam into a thin pencil beam, the focal point of beam being thefluorescent screen. Since the distance between the acceleration anodeand the screen varies generally linearly) the focusing field will bevaried in order to keep the focal point moving continuously on thescreen. It is possible to focus the beam magnetically instead ofelectrically, however, electrostatic focusing is preferred.

After focusing, the individual beams pass through the accelerating anodewhere high positive potentials give the electrons energy and velocitynecessary to produce visible light on the display screen.

As shown in FIG. 1, each beam thus formed, focused and accelerated isdeflected by a pair of deflection plates 30 and 31 which have properdeflection potentials applied thereto to cause the beam to traverse ahorizontal line of impingement 32 which is substantially parallel to oneside wall of the fluorescent screen 22. In general, in order to maintainuniform impact or impingement velocity as the beam is caused to traversealong the line of impingement, the beam must vary in angular velocity atits departure from the deflection plates 30 and 31. Hence, instead of aconventional saw-tooth deflection waveform, a parabolic shaped waveformis preferred such as shall be described more fully hereafter.

The multi-electron beam forming focusing and accel erating structureshown in FIG. l is shown in detail in FIG. 2 wherein a ilat header orclosure plate 35 has extending therefrom support posts 36, 37, 38, 39,respectively. Header plate 35 may form the end closure for a flatenvelope and all leads may project through header plate 35 by means ofconventional glass-metal seals, not shown. It is apparent that it is notnecessary or critical that leads from electrical supplies and/or controlpotentials exit from the tube through header plate 35 but they may exitfrom other portions of the tube. Cathode 25, grid structure 26, slottedplate 27, focusing and accelerating structure 29 and deflection plates30 and 31 are spaced along insulating support rods 3639 more closelythan is shown in FIG. 2, this spacing shown in FIG. 2 being for purposesof illustration only. Elongated cathode is supported by a pair ofsupport struts or straps 41 and 42 so that it is substantially parallelto header plate and, as described earlier herein, cathode 25 may Ibe ofthe indirectly heated or directly heated type, the leads for heatingelements not being shown in FIG. 2, it being understood that such leadsbeing carried to the outside of the envelope through conventionalglass-metal seals in header plate 35.

Control grid structure 26 comprises rectangular grid frame F, havinggrid wire posts P supporting a plurality of grid wires 26-1, 26-2, 26-326-410 each of which has a separate grid control lead 43-1, 43-2, 43-343-10, each grid lead exiting from the header plate 35 through aglass-metal seal, to provide pins 44-1, |44-2, 44-3, 44-10 forconnection to a control circuit to be described later herein. Spacedfrom grids 26-1, 26-2 26-10 is a slotted emission control plate 27having slot 28 therein which cooperates with the grid wires to defineindividual electron beams. A number of electrons drawn from the regionof the cathode by virtue of positive potentials supplied on a selectedemission grid element 26, pass through slot 28. It will be appreciatedthat there will be one beam for each line of the raster on screen 22.Each beam thus formed is focused and accelerated by focusing andaccelerating structure 29. Slotted plate 27 is mounted on insulatingsupport posts 36, 37, 38 and 39 by passing through mounting holes in theplate. As described earlier, conductors for supplying potential toemission plate 27 is by means of a conductor, not shown, passing throughthe header plate 35.

Focusing and accelerating anodes 29B and 29A may be constituted by apair of conductive plates 29A and 29B. Plate 29A has an aligned verticalrow of beam passages apertures 46-1, 46-2, 46-3, 46-N corresponding innumber, and aligned with the beam passing spaces between grid elements26-1, 26-2, 26-3 26-N. Likewise, plate 29B has a series of alignedapertures or passages 47-1, 47-2, 47-3 47-N, the passages 47 beingaligned with the passages 46 and defining therebetween focusing lensstructures for each individualized electron beam passing through slot28, respectively. The preferred forms of these elements are shown ingreater detail hereinafter but it suilices for present purposes to statethat these structures electrostatically focus and accelerate each beaminto a thin pencil beam and that the relative potentials between theplates 29A and 29B may be varied in order to dynamically maintain thepoint of focus of each individual beam, as it tranverses the line ofimpingement 32, at the point of impingement. Thus, as the beam impingesupon the screen 22 it will be continuously in focus. Dynamic focus indisplay tubes is well known in the art with respect to large areadisplays. However, since the variations are substantially linear intubes made according to this invention, the matter of dynamic focusingis simplified. It will also be understood that after focusing, the beampasses through the accelerating anode 29A and the applied high positivepotential on anode 29A give the electrons the energy and velocitynecessary to produce visible light on display screen 22. Finally, in asimplified form shown in FIGS. 1 and 2, the beam is caused to traversethe line of impingement 32 on display screen 22 by means of a pair ofdellection plates 30 and 31 which have proper dellecting potentialsapplied thereto. For example, the plate 30 may have a positive potentialapplied thereto so as to deflect the beam from travelling directlyparallel to the screen to where it impinges the display screen by meansof a stronger positive potential applied to plate 30` than is applied toplate 31. The orientation of dellection plates 30 and 31 and theelectron source structure shown in FIG. 1 project beams which wouldnormally impinge at varying acute angles as the bearn traversesfluorescent screen 22, so that due to this varying angle of impingement,the size of the light spot produced may vary according to the positionof the White spot along the line of impingement. However, this effect isobviated by structure and manner of operation to be described laterherein, it being the purpose ofthe present discussion to explain basicaspects of the invention.

With reference now to FIGS. 3, 4, 5, and 6, preferred forms of thefocusing and accelerating electrode structure 29 will be described. Withreference to FIG. 3, the focusing and accelerating anodes comprise a rstconductive metal plate 50 in which a series of holes or apertures 51-1,

51-2, 51-3 51-N have been drilled or otherwise formed and into each ofholes 51-1, 51-2, etc. is press fitted cylindrical metal tubes 52-1,52-2, 52-3 52-N,

respectively. Similarly, conductive metal plate 53 has a similar seriesof holes 54 into which similar cylinders 55 have been tted. Anode plates50 and 53 are separated by an insulating plate 56 made of mica, ceramicor other insulating material which has elongated slot 57 of a length toaccommodate all of the holes 51-1, etc. and 54-1, etc. and these anodeplates may be adhered to or otherwise fixed in relation to each of theside block 56. The structure may then be supported by support posts suchas support posts 36, 37., 38, and 39 as shown in FIG. 2.

In practice, there is a large potential difference between the focusinganode 53 and accelerating anode 50- (several thousand volts). Thiscauses a fringing or convergentelectrical field to be set up between theinterior surfaces of the two coaxially aligned cylindrical anodes. Theconvergent electrical field lines between the pairs of anode cylindershas a convergent lens effect on an electron beam passing through thecylinder pair and by holding the voltage on the accelerating anode 53constant (to maintain the velocity of the electrons constant) andraising or lowering the voltage on the focusing anode 50, the field canbe made more or less convergent. By varying the potential differencebetween the focusing anode 50 and the accelerating anode 53, the focuscan be continually changed through the horizontal sweep as the requiredfocal length shortens as the impact or impingement point of the electronbeam nears the multi-electron beam source. It should be noted that thepotential at both anodes are substantially constant with respect to thecathode. Further, it should be noted that the focusing characteristicsof every anode cylinder pair are identical at any time but that only theanode pair in which an electron beam is passing has any effect on thebeam focusing. As noted earlier, when the beams are grouped, andassigned independent display functions, the anode plates therefor may bemade .electrically separate for independent control.

Instead of using cylinders as described in connection with FIG. 3, theanode members (focusing and accelerating) may be made in accordance withstructure shown in FIG. 4. In this case, focusing anode 50 may be asolid block of metal 55 and the cylinders 52 being constituted by thewalls of the holes 51-1, 51-2' etc. Similarly, accelerating anode 53 maybe constituted by a similar block of metal having similar holes 54-1,54-2 etc. therein. Alternatively, the focusing and accelerationelectrode structure may be formed in accordance with the arrangementshown in FIG. 5 whereby the anode plates 50 are drilled with apertures51-1, 51-2 51-N", formed therein and cylinders 52-1, 52- and 52- arecarried therein, but not flush with one side or the other of the plates.Accelerating anode 53 has apertures and cylinder inserts similarlyformed, and insulator plate 56 is thickened somewhat to accommodate theprojection of the cylindrical inserts. Moreover, it is apparent that theanode cylinders may telescope, one within the other. In this case, thereis compensation for the capacity of the set that the inner faces of theanode plates 50 and 53" have for one another. FIG. 6 is a variantshowing the elimination of the insulative substrate 56, spacer posts 36,37", 38 and 39 being portions of support rods 36, 37, 38 and 39 of FIG.2, for example. It will be appreciated that the focusing andaccelerating anode structure may be made simply by boring aligned seriesof properly shaped holes in an insulating substrate and depositing orotherwise applying conductive metal surfaces thereon to form thefocusing lens and accelerating anode structure or a nonconductivesubstrate may be formed with opposed rows of cavities, filled withconductor material and the bored to provide electron beam passage. Thus,variation in lens design is possible within the framework of the presentinvention it being important that the structure has the focusing andacceleration characteristics desired herein.

It was mentioned earlier that when the electron beams are caused totraverse a line of impingement on the display screen, the angle ofimpingement, in accordance with the embodiment disclosed in FIG. l,varies as the beam is caused to traverse the line of impingement therebyvarying slightly the horizontal shape of the light spot as it traversesthe line of impingement. In order to eliminate and minimize this effect,the beams may be bent or deflected by a single deflection element or aplurality of deflection elements oriented in opposed relation to thedisplay screen. Thus, with reference to FIGS. 7, 8 and 9,

cathode 25, grids 26, and focusing and acceleration anodes 29, eg., themulti-beam forming structure, is deposed at an angle a (FIG. 7) to alineparallel to the display screen 22. In this instance, a planar deflectionplate or electrode 60, which may be a conductive coating on the rearWall v61 of envelope 20, cooperates with a deflection grid 62 to bend ordeflect the beam toward the display screen 22. (Although deflection grid62 is shown in the space between deflection electrode 60 and the displayscreen, it will be appreciated that grid 60` may be a transparentconductive coating on face plate 22.) Only one electron beam is shown inFIG. 7 but all beams have similar trajectories. In operation, as thelbeam leaves the accelerating and focusing anode structure 29, theelectron beam passes between deflecting plate 60 and deflecting grid 62the deflecting plate and the deflecting grid have applied thereto avarying electric field to establish a varying electrostatic fieldgenerally perpendicular to the direction of electron beam travel, e.g.,transverse to the direction of travel of the electron beam. If thedeflection plate 60 is negative and the deflecting grid 62 is madepositive the electrons will be deflected and accelerated toward thedeflection grid l62. This will result in the electron beam being bent ordeflected toward the deflection grid 62 and passing onto the gridstructure and striking the viewing portion or screen 22 to emit lightwhere the electrons strike. It is known that electrons projected througha region perpendicular to an electrostatic field follow a parabolictrajectory, so it can be seen from FIG. 8 that the angle x ofimpingement of the electron beam on display screen 22 can be held moreuniformly constant by making the configuration of the deflection plateconformal to a plate extending over the entire wall 61 of the tube and agrid 62 extending at least across the rear of the viewing screen. Asshown in FIG. 7, the angle of incidence or impingement is made even moreuniform if the electron beam is projected at a small angle a towards therear of the tube, e.g., at an angle of plus a to the display screen 22.As described earlier herein, focusing will be continually compensatedthroughout the sweep cycle by adjusting the focusing potential betweenthe focusing anode and the accelerating anode.

Further, it is believed that a uniform angle of impingement may beeffected by utilizing the continuous deflection plate 60 illustrated inFIGS. 7 and 8 by curving or canting the deilecting plate toward thescreen which will cause the electron path to bend only |gradually whilepassing through the region of the deflecting plates near the electronsource but to bend severely towards the far end of the deflection plate,thus, tending to equalize the impinging angle.

FIG. 9 is somewhat similar to the structure shown in FIG. 8 except hereinstead of a continuous deflection plate 60, the deflection element hasbeen broken up into a plurality of deflection elements '70-1, 70-2, 70-370-N (beam forming, focusing and accelerating structure 25, 26 and 29being shown separately in diagrammatic form). Deflection electrodes orelements 70 may be in the form of simple vertical or elemental stripesmade of transparent conductive material which may be deposited on anonconductive substrate or supporting surface, as for example, the rearwall of 61 of the tube.

As in the case of the embodiment shown in FIG. 8, the electron beamsentering the region between the deflection electrode elements 70 anddeflection grid 62 travel in a straight line to a point at which anelectrostatic eld has been established between one of deflectionelements 70-1, 70-2 70-N. By initially producing or establishing thiselectrostatic field near the far end of the tube remote from theelectron beam source, and moving the field by increments toward theelectron beam source, the beam may be made to traverse the displayscreen much in the same manner as is described in detail in theaforementioned Aiken patent. This approach, of course, required anadditional sequential triggering or commutating circuit to be used tovary the defiection field across the face of the tube. However, thisdoes have the advantage that the angle of irnpingement stays veryuniform since the electron beam has very little deflection force appliedto it until it approaches near the vicinity of the impact or impingementarea of screen 22. FIG. 10 is a top view of the scanning device showingthe path of the electron beam in this modification.

FIG. 1l is a cross section view showing another modification of theinvention wherein two or more electron sources, at least one on each endof the tube are utilized to provide horizontal scanning. In thisinstance, a first multi-beam source A, identical to ones describedearlier herein, projects its beams from left to right Whereas a secondmulti-beam source B projects its beams from right to left (or viceversa). Multi-beam source A may, for example, be arbitrarily designatedas the beam source to supply odd-numbered horizontal traces whereasmultibeam source B may be arbitrarily designated to supply even-numberedhorizontal traces to thus provide interlaced scanning. In this way, anylengthening or change in light spot shape or dimension will be adjacentto a shortened light spot so that this has the tendency to blend orcompensate the two images together and the picture will appear. Analternate practice would be to superimpose the two traces and reduce theintensity of the traces. In this way, bright spots, in order to appearvery bright, would have to be made of two light traces superimposed uponeach other. As can then be seen, only the narrow part of the beam willshow clearly and the broad part of the beam will be rendered onlyfaintly visible, if at all. A further compensation would be to intensifythe electron beam from the source near the present position of the tracewhile weakening the electron beam from the other source.

It should be appreciated that in connection with FIG. 1l showing thesecond multi-beam source, that greater resolution may be effected byproviding more horizontal lines. Thus, alternate scanning coupled withinterlaced scanning can be accomplished. In alternate scanning, onesource, source A for example, could supply lines 1, 5, 9, etc. and lines2, 6, 10, etc., while the other source, source B, would supply lines 3,7, 11, etc. and lines 4, 8, 12, etc. This expedient could simplify theconstruction of small size television tubes. Of course, each beam sourceis offset vertically (relatively) with respect to beams from an oppositesource. It will likewise be apparent that use of plural multi-beamelectron sources makes it easier for an electron beam to irnpinge upon adesignated phosphor for any color television tube (as shown, for examplein FIG. 23). For interlaced scanning, typical proximate waveforms areshown in FIGS. 12, 13 and 14. In FIG. 12, the approximate waveform usedfor sweeping the trace from the source B through interlaced scanning isillustrated, and FIG. 13 shows the approximate waveform used to sweepthe beam emitted from source A while interlaced scanning is utilized,whereas the waveform illustrated in FIG. 14 would be used for alternatescanning. It is not necessary that the beam source or sources be locatedto the right or left side of the screen, illustrations heretoforedescribed being merely illustrative. In fact, it is contemplated thatthe electron beam source run along the bottom of a display screen, e.g.,the elongated cathode running horizontally along with the associatedemission control structure and the focusing and acceleratin-g structure.In fact, this may be advantageous where the vertical dimensions of thedisplay screen is less than the horizontal dimension. Thus, simplyprojecting the beams upwardly while moving the electron emission pointfrom left to right, the vertical elongation of the trace, may be of lessmagnitude than the horizontal elongation of the trace due to varyingangles of impingement simply because of the lesser distance involved. Ofcourse, in this approach, the electron beam will be turned off and on,being displaced stepwise during off times so as to trace an imagecomposed of a rectangular array of dots in a pattern much like a halftone newspaper photograph. Functionally, such beams would be projectedupward to a certain elavation, the beam would traverse from left toright and then be cut off. Then, the beam would be projected upward to apoint slightly lower than the previous trace and then traverse ahorizontal line from left to right and repeat. Moreover, there may bemultiple beam sources at the right and left side of the screen as wellas along the bottom (and top if desired) so as to effect color display(FIG. 23), the beams from the respective sources seeking out their owncolor phosphors from different directions.

The embodiments described above are indirect displays in that the beamsstrike the phosphor of the display screen on a side or surface oppositethe viewing side or surface. In accordance with the embodimentillustrated in FIGS. 15-20, the phosphor display screen is viewed fromthe side or surface struck by the electron beams. In FIG. 15 themulti-beam source designated generally with the numeral includescathode, emission control structure and focusing and accelerating anodestructure as described earlier herein. Likewise, as described earlier,the electron beams enter the region between the dflection plate 71 anddeflection grid 72 and is deflected thereby in amounts and directionaccording to the direction of the electrostatic field between thesedeflection elements. The present arrangement differs from thosedescribed earlier herein in that the deflection plate 71 is in the formof a conductive layer deposited on a nonconductive substrate or supportsurface, such as the rear wall or panel of the tube. In this case,however, the fluorescent phosphor (not shown) is deposited directly uponthis conductive layer. Further, the deflection plate 71 has a positivepotential applied thereto Whereas the defiection grid 72 may have anegative potential applied thereto or even so that in effect electronbeams are directed to impinge upon the fluorescent phosphor screen andthe image may be viewed through the deflection grid 72. Due to the highincidence of peripheral light, the grid will not be particularlynoticeable. In any event, the grid may be applied to the interior tubesurface 73 in the form of transparent conductive material (and in somecases both deflection electrodes may be applied on exterior envelopesurfaces). The advantage of this construction and manner of operationlies in its reduction of the amount of energy usually required toproduce an equivalent amount of light output and more efficientutilization of light produced. Conventionally, an electron beam strikeson the screen with high velocity and has to force its way through ametallic layer into the phosphor coating in order to create light. Thelight energy discharged then has to travel through the phosphor to emitvisible light that can be seen by the viewer. By bombarding the surfacewhich is to be viewed instead of the non-viewing surface, significantsavings in energy can be obtained and the energy available is moreeffectively utilized. In addition, lower electron velocities can 4beutilized and therefore lower focusing and deflecting potentials arerequired, all with attendant benefits in making the equipment portableor operable from low energy sources and the utilization of smallercomponents. FIG. 16 is a diagrammatic view of the arrangement shown inFIG. 15, the observer being designated O. It will also be appreciatedthat instead of a single deflection plate 71, multiple deflectionelements illustrated in FIG. 9v may be utilized and this isdiagrammatically illustrated in FIG. 17.

FIGS. 18 and 19 are modifications of the embodiment illustrated in FIG.7 to illustrate applications of the direct view principle illustrated inFIGS. 15 and 16 with the multi-beam source 80l being contained within anoffset section 20S of the tube 20. FIG. 20` is a further illustration ofthe modification of the invention shown in FIG. 7 as applied to thedirect view principle described herein.

With respect to FIGS. 18 and 19, offset 20S has been introduced into thetube 20 in order to get the multi-beam electron source or gun 80 angledto place the point at which the electrons exit the accelerating anodeflush with the viewin-g screen 2-2. The reason for this is the fact thatan electron entering an electrostatic field follows a parabolic path. Ifthe screen surface is flush with the electron gun, the electron ray willstrike the screen at the same angle with which it enters the field nomatter what portion of the screen it strikes. In other words theimpinging angle of the electron beam remains constant as the point ofimpingement varies across the screen.

Calculations were made for a tube with a display area of 45 cm. x 30 cm.(17 in. x 11.8 in.). Results indicated that a tube measuring 6 cm. (2.35in.) from front to rear face could accommodate a projection angle of24.4 (say 20-25 A tube measuring 8 cm. (3.15) could accommodate aprojection angle thus on equal impinging angle of 31.1 (say 25 31 Whilea little steeper angle is preferred, a 30 angle is satisfactoryparticularly if the electron beams instead of being formed ofessentially circular cross sectional area were to be shaped of arectangular or elliptical nature with the major axis running vertically.

lReferring to FIG. 20, between the viewing screen 22 and the deflectionplate 71". There is .a deflection grid 72D substantially flush with thebeam emission end of the multi-beam electron gun '80' and the gun isaimed to the rear of the tube. The electron bea-m will return to theregion of the deflection grid 72D at the same angle at which it enteredthe field between the deflection grid and the deflection plate. For adistance of 4 cm. 1.58 in.) between the deflection grid 72D anddeflection plate, the entry (and exit) angle is about 20. [Anotherelectrostatic field shall be formed between the deflection grid 72D andthe screen 22 and deflection electrode 71. Since the electron beamalways enters this field at the same angle (about 20) if the fieldbetween the deflection grid and screen is kept `at a constant intensitythe electron beam will always follow the same behavior in this field.This means that the electron beam will always strike the screen at thesame angle.

To recapitulate, the electron beam enters the -field between thedeflection grid and deflection plate at a constant angle, travels in aparabolic trajectory and exits the eld at the same angle with which itenters. Upon entering the second field between the screen and deflectiongrid, the electron beam still travels a parabolic trajectory, but adifferent parabola. If the field between the screen and deflection gridremains steady with respect to time, the electron beam shall alwaysfollow an identical path Ibetween the deflection grid and screen. Thus,if the angle of entry into the field never varies, the angle of exit (orimpact angle on to the screen) never varies.

Using a distance of 2 cm. (.79 in.) from the deflection grid to thescreen and on entry angle of 20 potential of 4,500 volts between screenand grid produces an impact angle of about 45 onto the screen. Apotential of 30,000 volts between screen and grid produce lan angle ofimpingement of 75 which is nearly vertical. An angle between 45 and 75should certainly be acceptable. Thus a tube thickness of 6 crn. (2.36in.) and smaller is achieved. Of course, where this back `aiming is notused the tube thickness will be smaller.

Horizontal sweeping shall be accomplished by varying the voltage betweenthe deflection plate and deflection grid. The voltage between thedeflection grid and the screen shall remain constant.

lIt will be appreciated that the multi-beam source and method describedherein may be utilized for many types of display systems, as forexample, to reproduce fixed characters and/or other shaped images orscoreboard columns, computer readouts, metering devices, wherein a flatdisplay is desired.

The tube structure and multi-beam scanning devices described earlierherein may be effectively utilized by adapting circuitry well known inthe art. In order to illusstrate this, reference is made to FIGS. 2l and22. Specifically, FIG. 21 is a block diagram of external circuitryassociated with a display device of the present invention as appliedwith respect to conventional television signals. Thus, a receivingcircuit includes a conventional antenna 90, for receiving conventionaltransmitted television signals and supplying same to receiver circuit91. The receiver circuit 91 contains the conventional devices for hometelevision receivers, for example, such as the usual RF and IFamplifying sections, detecting and control circuits and standard audiocircuitry. Picture information is fed from receiver circuit 91 to videoamplifier 92 and video amplifier 92 applies amplified video signalbetween emission control plate yand the cathode to control the intensityof a beam and, accordingly, the brightness of the trace in essentiallythe same manner as effected in conventional television receivers. Withreference to FIG. l the video information is applied between emissionplate 27 and cathode 2S. As noted earlier, the audio circuitry isconventional and since it has no part in the present invention, it isnot disclosed herein.

Further, control information is fed from receiver circuit 91 to syncseparator circuit 93 from which horizontal sweep pulses are applied tohorizontal sweep generator 94 which produces the horizontal sweepvoltages applied to the deflection plates.

Vertical sync pulses are also fed from the sync separator circuit 93 tothe grid controlling circuit 95 described in greater detail inconnection with FIG. 22. IIt should be noted at this point that if aring counter type circuit is used as a grid controlling device,horizontal sync pulses can be used to trigger the grid controllingcircuit and the vertical sync pulses may, for the most part, be ignored.

As noted earlier herein, the focus will be continually modified so as tocompensate for the different distances from the acceleration anode to apoint of impingement on the screen so periodically varying voltages willybe applied across the accelerating and focusing anodes. Accordingly, anoutput from the sync separator circuit 93, the horizontal sync pulsesare utilized to trigger a focus cornn pensation generator 96 whichproduces a varying voltage applied to the focusing anode. Alternatively,control of focus compensation circuit 96 may be obtained from thehorizontal sweep generator, as is shown by connection 89..

With reference now to FIG. 22, vertical sync pulses from sync separator93 are fed into a bistable multivibrator 97 which is control gate forcontrolling a pair of ring counters 98 and 99, respectively, which areused to effect sequential switching of the control grids, one ringcounter circuit 98 being utilized to control odd numbered grid elementsand the other ring counter 99 being used to control even numbered gridcircuits, depending on the steady state condition of control flip-flop97. As shown in FIG. 22, outputs of the ring counters are appliedthrough coupling circuits, such as transistor followers T1, T3, T5 etc.,to the grid elements. Thus, if pulses are fed into ring counter 98, thepulse signal will sequentially pass from coupling transistor T1, T2, T3,T4 etc., for the total number of stages desired and then on theactivation of the final stage in the ring counter, the control flip-flopgate circuit 97 will be reset into its other steady state condition tothereby permit counter pulses to pass through the gate into ring counter99 and control the interlacing of scan line. In operation, lalltransistors except a selected one are off so a negative potential V) hasbeen placed on these grid wires. With the selected transistor on, thegrid connected thereto has a positive potential with respect to thecathode to permit electrons to flow in the region of the grid wirehaving the positive potential.

It will be appreciated that instead of using a control gate such asflip-flop 97, a single shift register with odd numbered control gridsconnected in sequence to the first l l stages of the shift register andthe even sequence of control grid wires Connected to the last half ofthe shift register with the last stage of the shift register producing afeedback signal for resetting the shift register to re-initiate thesequence may be used.

Use of integrated circuitry reduces the size of this eX- ternalcircuitry to very small dimensions. It is possible that other logic typecircuitry may be used to control the grid voltages such as binarycounters, delay lines, time delay circuits etc., and the like or acombinaton of these circuits the only essentiality being the sequentialcontrolling of the `grid voltages.

FIG. 23 shows the rear surface of a television screen 122 with threelinear multi-beam cathodes (control grid and focusing and acceleratingelectrodes being omitted for clarity) arranged along the sides and thebottom and designated Blue, Red, and Green. The screen 122 is composedof a plurality of four sided pyramid shaped structures 123 which havebeen formed by molding, etching, grinding or any other processindigenous to the glass markers art. The left side or facet of thepyramids (as seen in FIG. 23) are coated by a phosphor material thatemits blue light when excited by an electron beam. The right side orfacet is coated with a phosphor that emits red light and the bottom sideor facet is coated with a phosphor that emits green light so that anycolor is produced by the combination of the three colors.

As can be seen, it is impossible for any electron beams emitted from saythe red multi-beam source to strike anything other than a red lightproducing phosphor. Therefore shadow masking and other methods used tokeep the red on red, green on green etc. are dispensed with. Mixing ofcolors by varying intensity of the electron beams can be done withconventional color TV circuitry.

Scanning can be done by either sending the chrominance informationthrough a frequency trippler circuit and scanning alternately red, blue,green thereby rendering each image field composed of 3 subfields andeach frame composed of 6 subfields. Or scanning may be accomplished byeach color gun projecting its respective beam simultaneously and havingthe three beams converge toward a single area where a strong field isset up between the screen and deflection plate. This will requiresegmenting the deflection plate both horizontally and vertically, butcontrol of the potential across each individual segment of thedeflection plate can be made auxiliary to the circuits controlling thegrids of each cathode.

FTG. 24 illustrates another method for producing a color picture is toutilize only one multi-beam electron gun and have alternate strips ofred 130, green 131, and blue 132 light producing phosphors deposited onthe screen in horizontal lines. Behind each red strip and behind eachblue strip, there is a horizontal wire. The wires behind the red stripsare connected together by but 135 and the wires behind the blue stripsare connected together by bus 136. The end leads 138 and 139 of thesecondary 137 of a center tap transformer are connected, end 138 to thered wires, and end 139 to the blue wires, respectively. A largepotential difference is placed between the center tap 140 and the screen(not shown). The primary (not shown) of the transformer is excited withan AC voltage of 3.58 megacycles. As seen in FIGS. A, 25B and 25C, whenthe AC signal is going through zero the beam falls only on a greenstripe. The color information for green only is placed across themulti-beam electron gun at this time. When the signal swings towardpositive on the blue wires, only the blue stripe is illuminated and atthis time only the blue color information is placed on the electron gun.When the signal swings toward positive on the red wire only the redcolor is displayed and only red color information is placed upon theelectron gun.

The 3.58 megacycles signal causes the electron beam to oscillatevertically as it traverses the screen horizontally as can be seen byFIG. 25. The green portion of the color picture is excited twice asoften as the red and blue colors, but for only half as long. Thisnecessitates that the green color information 'be run through afrequency doubler and this signal used to gate the electron beam. Thismethod of color reproduction is the method used on the ychromation orLawrence type tube and is only briefiy described herein for purposes ofillustrating the wide utility of the invention.

While there has been shown and described in detail the fundamental novelfeatures of the invention, it will be understood that many variationsare possible, some of which have been disclosed herein, and that Variousother modifications and changes in the form and details of the inventionmay be made by those skilled in the art without departing from the scopeand spirit of the invention.

I claim:

1. In a flat cathode ray display tube a flat envelope having front andrear walls and having an electron responsive display screen adjacent awall thereof, a multibeam electron gun assembly for producing aplurality of individually controllable electron scanning beamsprojectable along parallel paths between the said front and rear walls,respectively, to impinge on said display screen along lines ofimpingement, respectively, comprising,

an elongated electron emissive cathode at one side of said envelope,

control electrode means for controlling the intensity of electronsemitted from said elongated cathode,

a grid structure for controlling emission of electrons from said cathodeat any selected point along the length thereof, said grid structurebeing between said elongated cathode and said control electrode means,

focusing and acceleration electrode means for focusing and acceleratingelectrons emitted from any selected point on said elongated cathode,said focusing acceleration electrode means including a pair ofconductive plate members supported in spaced relation to each other,each plate having a plurality of apertures therein aligned with saidelongated cathode, the number of apertures in each of said platescorresponding to the number of lines of impingement upon said displayscreen, and

means for deflecting a selected beam issuing from any of said focusingand acceleration electrode means onto said display screen and totraverse a line of impingement.

`2. The invention defined in claim 1, wherein said apertures areconstituted by conductive cylindrical members affixed to each plate.

3. The invention defined in claim 1, wherein said multibeam electron gunas-sembly is aimed at a direction greater than but less than 210 withrespect to said display screen.

4. The invention defined in claim 1, wherein said means for deflectingincludes deflection electrodes oriented so that any defiection fieldestablished between them is substantially normal -to the plane of saiddisplay screen and wherein said multi-beam electron gun is aimed at adirection toward said -the rear wall of said tube and away from saiddisplay screen.

5. The invention defined in claim 1, wherein said display screen ispositioned such that it -is viewed from -the surface thereof impingedupon by the electron beams.

`t5. The invention dencd in claim 1, including at least one further ofsaid multi-beam electron gun along another side of said display screen,

said display screen being constituted of a plurality of multifacetedprotuberances, with at least one facet facing in a direction to beimpinged upon by `only one beam from one of said multi-beam sources andat least one facet facing in a direction to be impinged upon by only onebeam from the other of said multibeam sources,

'and each of said facets facing a multi-beam source having a differentcolor producing phosphor thereon.

7. In a flat multi-beam display tube having a display screen, anintegral focusing and acceleration electrode structure for ea-ch beam,comprising,

an elongated mul-ti-electron beam source,

a first elongated conductive planar member having a .plurality ofpassages therein each such passage being aligned with one of the beamsfrom said multi-beam source, respectively,

a second elongated conductive planar member having a plurality ofpassages therein corresponding in number to the number of passages insaid first conductive planar member, each passage in said secondconductive planar member being coaxially aligned with a correspondingpassage in said first conductive planar member,

means mounting said conductive planar members `in spaced apart relationwith respect to each other and said multi-beam source,

means applying a fixed high electron beam accelerat- -ing voltage to thesecond of said planar members with respect to said source,

means for applying a variable lower po-tential to said first conductiveplanar member,

whereby a variable converging electrostatic beam focusing lens is formedfor each individual beam of said multi-beam source between surfaces ofsaid aligned passages, respectively, and ya substantially uniformacceleration force is applied to all beams exiting from passages in saidsecond conductive planar member.

8. The invention defined in claim 7, wherein said passages areconstituted by conductive tube members secured to said conductive planarmembers.

9. The invention defined in claim 7, wherein said elongated multi-beamsource includes an elongated heated cathode member capable of emittingelectrons along its length,

`a plurality of grid wires transverse to the long dimension of saidelongated cathode,

means for applying to each of said grid wires, individually, a beamcontrol and switching potential,

a planar conductive member commonly spaced from all of said grid wires,and

means for applying `intensity modulating potentials to the last namedplanar conductive member.

10. The invention deiined in claim 7, wherein said display screen ispositioned such that it is viewed from lthe surface thereof impingedupon by the electron beams.

11. The invention defined in claim 7, wherein said means mounting saiidconductive planar members in spaced apart relation includes anonconductive substrate, one of said conductive planar members being onone side of `said nonconductive substra-te and the other of saidconductive planar members being on the other side of said nonconduc-tivesubstrate, said substrate having electron passage means therein.

12. The invention defined in claim 11, wherein said conductive planarmembers .are constituted by conductive platings on said nonconductivesubstrate, said passages being constituted by plating o-n walls ofapertures formed in said substrate transverse to Ithe surfaces of saidnonconductive substrate.

13. The invention defined in claim 7, including means for establishing abeam dee-ction field normal to said display screen, said secondconductive planar member being oriented with respect to said de-ectionfield such that electron beam-s exiting from apertures in said secondconductive member, if undeflected, travel in a direction away from saiddisplay screen.

14. The invention defined in claim 13, wherein any electron beam exitingfrom said second conductive planar member is caused to traverse aplurality of parabolic paths to said display screen each parabolic pathbeing according to the field strength of said deflection eld.

15. A method of producing an image on a display screen in an evacuatedfiat envelope having an elongated source of electrons at one -side ofsaid envelope, said elongated source of electrons having a length atleast equal to one length dimension of the image to be produced on saiddisplay screen, comprising the steps of:

permitting electron emission from said source from a first selectedpoint along its length for a predetermined period of time and preventingelectron emission from other selected points along the length of saidsource during sadi predetermined period of time,

intensity modulating said electron emission from said first selectedpoint,

simultaneously accelerating and focusing the beam elctrons emitted fromsaid first selected point, deliecting said beam of electrons emittedfrom said first selected point to impinge upon said display screen alonga line of impingement, sequentially terminating emission from saidselected point and initiating emission from another selected point onsaid elongated cathode, and modulating, accelerating, focusing, anddeflecting each succeeding beam whereby a plurality of lines ofimpingement are traversed on said display screen, ea-ch line ofimpingement being traversed by one of said beams emitted from a selectedpoint on said elongated source, respectively.

16. The method defined in claim 15, wherein said display screen ispositioned with respect to paths of said beams that the surface of saiddisplay screen is impinged upon by said beams is the screen viewingsurface seen by an observer.

17. 'Ihe method defined in claim 15, wherein said steps of deflectingincludes establishing a plurality of deflection fields, each insequence, and each being oriented in a direction normal to the plane ofsaid display screen.

y18. The method defined in claim 15, wherein t-he steps of deecting abeam includes,

establishing a deflecting field having a direction normal to saiddisplay screen,

the steps of permitting electron emission, simultaneous `acceleratingand focusing, include aiming beams from selected points in a directiongreater than but less than 210 to the direction of said deliect- `ingfield.

19. The invention defined in cl-aim 18, wherein said display screen ispositioned with respect to paths of said beams that the surface of saiddisplay screen impinged upon by said beams is the screen viewing surfaceseen by an observer.

20. The invention defined in claim 18, including the step ofestablishing a fixed electrical guiding field for guiding deflectedbeams to substantially uniform angles of impingement on said displayscreen.

References Cited UNITED STATES PATENTS 2,449,339 9/ 1948 Sziklai 315-1312,795,731 6/ 1957 Aiken. 2,858,464 10/ 1958 Roberts. 2,904,722 9/1959Aiken. 3,176,184 3/1965 Hopkins 315-13 `5,226,596 12/1965 Kasperowicz.

RICHARD A. FARLEY, Primary Examiner M. F. HUBLER, Auxiliary Examiner

